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A control valve is a valve used to control fluid flow by varying the size of the flow passage as directed by a signal from a controller. [1] This enables the direct control of flow rate and the consequential control of process quantities such as pressure , temperature , and liquid level.
The distinguishing feature of the PID controller is the ability to use the three control terms of proportional, integral and derivative influence on the controller output to apply accurate and optimal control. The block diagram on the right shows the principles of how these terms are generated and applied.
Simple hydraulic control valves are binary, they are either on or off. Servo valves are different in that they can continuously vary the flow they supply from zero up to their rated maximum flow, or until the output pressure reaches the supplied pressure. More complex servo valves can control other parameters.
The crankcase air outlet, where the PCV valve is located, is generally placed as far as possible from the crankcase breather. For example, the breather and outlet are frequently on opposite valve covers on a V engine, or on opposite ends of the valve cover on an inline engine. The PCV valve is often, but not always, placed at the valve cover ...
The hydraulic actuators respond to changes of pressure or flow and will open or close the valve. Automatic control valves do not require an external power source, meaning that the fluid pressure is enough to open and close them. Flow control valves, a type of automatic control valve, regulate fluid flow by maintaining a predetermined flow rate ...
A back-pressure regulator, back-pressure valve, pressure sustaining valve or pressure sustaining regulator is a control valve that maintains the set pressure at its inlet side by opening to allow flow when the inlet pressure exceeds the set value.
A rotary valve (also called rotary-motion valve) is a type of valve in which the rotation of a passage or passages in a transverse plug regulates the flow of liquid or gas through the attached pipes. [1] The common stopcock is the simplest form of rotary valve. Rotary valves have been applied in numerous applications, including:
Schrader valve components (from left to right) the valve core closed (top) and open (bottom), the order of assembly, end view of stem without core and with core (top) and stem with the dust cap on (bottom). The core has a short outer thread which is screwed into the inner thread of the stem. The visible outer thread of the stem holds the dust cap.